The original alfaerie set should be considered obsolete now that we have alfaeriePNG, and its use should be discouraged. The anti-aliased version looks so much better. But the anti-aliasing causes pixels on the boundary of the black outline and the colored interior to be darker versions of the interior color, by mixing in the black. So simply looking for an exact match of the original color fails to replace the boundary pixels. This problem can be solved, though: you could test every pixel for the value of the briggtest RGB component, and deduce from that by which factor it is darkened compared to the interior color. And then darken the replacement color by the same factor. (This assumes the outline is pure black.) To make it resistant to multi-color originals you could even check whether the other two RGB components of the original are indeed similarly darkened (within some tolerance for rounding.)
The original alfaerie set should be considered obsolete now that we have alfaeriePNG, and its use should be discouraged. The anti-aliased version looks so much better. But the anti-aliasing causes pixels on the boundary of the black outline and the colored interior to be darker versions of the interior color, by mixing in the black. So simply looking for an exact match of the original color fails to replace the boundary pixels. This problem can be solved, though: you could test every pixel for the value of the briggtest RGB component, and deduce from that by which factor it is darkened compared to the interior color. And then darken the replacement color by the same factor. (This assumes the outline is pure black.) To make it resistant to multi-color originals you could even check whether the other two RGB components of the original are indeed similarly darkened (within some tolerance for rounding.)